It is known to blend flexible coil polymers with either liquid crystal homopolymers or liquid crystal random copolymers. A recent review of work in this field is "Polymer Blends Containing Liquid Crystals: A Review", by D. Dutta et al., Polymer Engineering and Science, Mid-September 1990, Vol. 30, No. 17, pp. 1005-1018. The Dutta et al. publication (on pages 1008-1011) discusses certain prior work by Joseph et al. and Misra et al., for example, in which poly(ethylene terephthalate), PET, was used as the matrix material and was mixed with a liquid crystalline copolyester based on parahydroxy benzoic acid (PHB) and PET. In such systems, the flexible coil polymer component (PET) in the liquid crystal polymer was the same as the PET matrix. Dutta et al. also report that Kimura et al. blended a poly(butylene terephthalate), PBT, matrix with a PET/PHB liquid crystal copolymer.
European Patent Publication No. 390,489 shows blends of a crystalline polyalkylene arylate base resin, which in Example 4, can be PET with a random copolyester having a polyalkylene arylate segment which exhibits smectic liquid crystallinity and a polyalkylene arylate segment which does not exhibit smectic liquid crystallinity. This liquid crystal copolyester is derived from the copolymerization of dimethyl terephthalate, dimethyl bibenzoate, and 1,4-butanediol. With such random copolymer additives, the blending operation can readily give rise to transesterification between the matrix and flexible coil polymer moieties in the copolymer.
Quite recently, in contrast to the foregoing systems which rely upon blends of a flexible coil polymer matrix with either a liquid crystal homopolymer or random copolymer, it has been found that a blend can be fabricated from a flexible coil polymer matrix and a thermotropic liquid crystal segmented block copolymer containing mesogenic and flexible coil polymer blocks (as described in U.S. Ser. No. 726,600, filed Jul. 8, 1991). The flexible coil blocks were deemed essential in order to lower the melting point of the liquid crystal-containing additive. For those systems, it was taught that the flexible coil blocks in the block copolymer had to be substantially similar to the composition of the flexible coil polymer matrix, i.e., a PBT matrix and a PBT flexible coil polymer matrix. That application indicates that selection of a PET matrix requires selection of a PET flexible coil block segment. In such block copolymer systems it was perceived that there was a critical need to very closely match the matrix polymer with the flexible coil polymer block segment in the liquid crystal additive in order to enhance compatibility of the blend components.
One fairly recent U.S. patent which describes liquid crystal fiber-reinforced polymer composites and the process for making them is U.S. Pat. No. 4,728,698 to A. Isayev.